Exhaust Gas Temperature Control via Segmented NO2 Flow
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Solution Overview
Problem
Particle filters in internal combustion engines, especially in lightly loaded engines, face challenges with unreliable regeneration due to limited NO2 formation at high temperatures, leading to increased back pressure and fuel consumption, and risk of thermal damage during active regeneration.
Innovation Solution
A method and device that combines parallel flow of an NO oxidation catalyst and a heated catalytic converter to increase exhaust gas temperature before the particle filter, using a separate heated gas flow to maintain NO2 availability and avoid excessive hydrocarbon concentrations, allowing for a combination of active and passive regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the exhaust gas temperature is actively raised by adding hydrocarbons to oxidize soot, then soot oxidation is improved, but the temperature increases to over 600°C which reduces NO2 formation and may cause thermal damage to the particle filter and catalytic converters
Solution Approach 1:
The exhaust gas flow is divided into two separate streams: one passing through the NO oxidation catalyst to generate NO2, and another passing through the heating device to increase temperature. These segmented streams are then combined downstream, allowing temperature increase without compromising NO2 formation, thus resolving the contradiction between reliable soot oxidation and excessive temperature rise
Solution Approach 2:
A mixing section is introduced as an intermediary between the NO oxidation catalyst and the heating device. This intermediary allows the hot gas stream and the NO2-rich stream to combine without direct thermal interaction that would harm NO2 formation, enabling both high temperature and high NO2 availability for effective soot oxidation
2Temperature
If hydrocarbons are added upstream of the NO oxidation catalyst to raise temperature, then active regeneration is achieved, but NO2 formation is significantly reduced due to thermodynamic limitations at high temperatures
Solution Approach 1:
The exhaust gas flow is segmented into two separate paths: one through the NO oxidation catalyst for NO2 generation, and another through the heating device for temperature increase. This segmentation ensures that NO2 formation occurs in a separate zone from the high-temperature region, maintaining high NO2 concentration while achieving the necessary temperature for soot oxidation
Solution Approach 2:
The gas stream is pre-heated in a separate path before combining with the NO2-rich stream from the NO oxidation catalyst. This preliminary heating action occurs without compromising the subsequent NO2 formation, as the heating takes place in advance in a separate flow path, allowing both high temperature and high NO2 availability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach shortens regeneration time, reduces hydrocarbon requirements, and minimizes thermal damage, achieving reliable and efficient particle filter regeneration at lower temperatures, around 400°C, while maintaining NO2 availability for effective soot oxidation.
Implementation Method 1
at least one NO oxidation catalyst arranged upstream of the particle filter for oxidizing NO, in particular to form NO2
Implementation Method 2
a heating device through which a further gas flow flows, which is formed in particular by at least one heated catalytic converter, by means of which the further gas flow is heated
Implementation Method 3
this heated further gas flow then being treated upstream of the particle filter with a gas coming from an NO oxidation catalytic converter, in particular loaded with NO2, exhaust flow is mixed
Implementation Method 4
the NO2 reacts in the particle filter with the carbonaceous ultra-fine particles to form CO, CO2, N2 and NO
Data Source
AI summary
The invention relates to a method and a device for regenerating a particulate filter arranged in the exhaust tract of an internal combustion engine, with at least one NO oxidation catalyst arranged upstream of the particulate filter for the oxidation of NO, in particular to NO2, through which an exhaust gas stream flows. According to the invention, at least one heating device (8), in particular a heating catalyst, is arranged upstream of the particulate filter (3) and through which a further gas stream, or a second exhaust gas stream (14), flows. The further gas stream (14) is heated by means of which the further gas stream (14) is heated, and the heated further gas stream (14) is mixed upstream of the particulate filter (3) with the exhaust gas stream (15) coming from the NO oxidation catalyst (6), in particular the exhaust gas stream loaded with NO2.